1. Field of the Invention
The present invention relates to an apparatus for reproducing data from an optical disc, and more particularly, to an apparatus for reproducing data from an optical disc in which a disc inducing vibration is detected and its speed is converted into an appropriate reproducing speed.
2. Description of the Related Art
Generally, an apparatus for reproducing data from an optical disc which is revolved by a motor can cause serious vibration according to the state of a medium, or cannot read recorded data due to the instability of a servo state.
The existing apparatuses for reproducing data from an optical disc typically operate by using a vibration sensor or actuator back electromotive force to detect the disc inducing vibration.
For example, an apparatus for reproducing data from an optical disc having a vibration sensor increases the speed of a spindle motor so that the revolution speed of the disc is lowered as a function of the amount of a detected signal.
Furthermore, an optical disc reproducing apparatus may operate by using back electromotive force to increase the speed of a spindle motor so that the revolution speed of the disc is lowered by back electromotive force induced in an actuator. Such a disc operates by: 1) increasing the number of revolutions of the spindle motor to a target number of revolutions per minute (RPM); 2) switching focus and tracking to “OFF” states; 3) amplifying back electromotive force induced in a tracking coil and then converting from analog to digital; 4) switching focus and tracking to “ON” states.
However, the optical disc reproducing apparatus using the above vibration sensor is disadvantageous because sensing ability varies with the point of attachment of a vibration sensor, and also with respect to the assembled state of the apparatus. Furthermore, the optical disc reproducing apparatus using actuator back electromotive force requires a comparator for checking actuator back electromotive force. This is disadvantageous because considerable time is spent checking a vibration-inducing disc after focus and tracking are in the “OFF” state. A further disadvantage of this method is that a certain speed factor is constant when a vibration-inducing disc is checked.